1. Field of the Invention
The present invention relates to a position detection apparatus which detects a relative position between two different objects, an imprint apparatus, and a position detection method.
2. Description of the Related Art
Imprint technology is technology for forming a fine pattern on a substrate by using a mold having a pattern. For example, such an imprint technology includes photo-curing method. In the imprint technology using photo-curing method, first, a resin (imprint resin, photo curable resin) which serves as an imprint material is supplied to a shot which serves as an imprint region on a substrate (wafer). The resin is cured by bringing the resin into contact with a pattern of the mold (imprinting) and radiating light while the resin and the pattern are in contact with each other. The resin pattern is formed on the substrate by separating the mold from the cured resin.
When the resin on the substrate and the mold are imprinted, it is necessary to accurately align the substrate and the mold. In order to align the substrate and the mold in the imprint apparatus, a die by die alignment is performed by detecting marks formed in the mold and marks formed in the substrate in each shot is well known.
U.S. Pat. No. 7,292,326 discusses an imprint apparatus including an alignment mark detection mechanism for detecting marks used in an alignment. As the marks used in the alignment, diffraction gratings are arranged in each of a mold and a substrate. The diffraction grating in the mold side is a diffraction grating having a period in a measurement direction, and the diffraction grating in the substrate side is a checkerboard shaped diffraction grating having periods in each of a measurement direction and a direction orthogonal to the measurement direction (a non-measurement direction). Both an illumination optical system for illuminating the diffraction gratings, and a detection optical system for detecting a diffracted light from the diffraction gratings are disposed to be inclined from a direction orthogonal to the mold and the substrate toward the non-measurement direction. That is, the illumination optical system is configured to illuminate the diffraction gratings at an oblique incidence from the non-measurement direction. The light having entered the diffraction gratings at an oblique incidence is diffracted in the non-measurement direction by the checkerboard shaped diffraction grating disposed in the substrate, and the detection optical system is disposed to detect only a single diffracted light other than a zero-order diffracted light with respect to the non-measurement direction.
That is, U.S. Pat. No. 7,292,326 discusses a method in which only a single diffracted light is detected. Accordingly, an amount of diffracted light from the diffraction grating is small, and it is difficult to detect a mark used for alignment.